1. Field of the Invention
The invention relates to an LED lamp. In particular, the invention relates to LED lamps for use in general applications, including vehicle lamps, street sign lamps, communication lamps, display lamps, etc. With regard to vehicle lamps, the invention relates to an LED lamp for a light source of a vehicle headlight which is used as an alternative to an incandescent lamp, a halogen lamp, or the like.
2. Description of the Related Art
FIG. 1 shows the configuration of a conventional headlight which uses an LED lamp as a light source. In this LED headlight lamp, LEDs are arranged in a matrix of three rows and eight columns to obtain prescribed brightness. A lens and the like are provided in front of the LEDs to obtain a desired light distribution characteristic. In the foregoing LED lamp, a plurality of chips may be enclosed (multi chip package) as necessary.
The LEDs with different colors are combined so that emission light is not tinted with a particular color. For example, the reference numeral 11 refers to LEDs emitting red light, reference numeral 12 refers to LEDs emitting green light, reference numeral 13 refers to LEDs emitting blue light, and reference numeral 14 refers to LEDs emitting yellow or white light (for example, see Translated Japanese Publication of International Application No. 2003-503815).
In the headlight having the conventional configuration described above, the plurality of LEDs, each of which has a beam-shaped light distribution characteristic, are combined to form the light distribution characteristic of the headlight. Thus, it is necessary to precisely align the orientation of the LEDs to even the light distribution characteristic of the individual LEDs. Accordingly, actual attachment requires high precision, and hence work operation becomes complicated and product yield is reduced. As a result, there is a problem in that costs are increased for the product.
When many LEDs are disposed in a large area, as described above, it is assumed that a necessary amount of light can be simply obtained as the total amount of light by calculation. It is difficult and almost impossible, however, to precisely orient light from the individual LEDs in a desired direction, so that it is also difficult or impossible to obtain a sufficient amount of light for brightly lighting up a distant location. Such an LED lighting device is available in signal lamps in accordance with current technology. As a lighting device such as a headlight, however, lighting at an attainable distance is insufficient even if the desired light distribution characteristic is obtained. Therefore, the LED lighting device is not commonly available in a headlight.
However, demand for a solid state light source is strong in recent years due to their low maintenance characteristics. Thus, it is desired to use LEDs as a light source in lamps, and particularly in a vehicle headlight.